As solar photovoltaic technology is adopted as an energy generation solution on an increasingly widespread scale, fabrication and efficiency improvements relating to solar cell efficiency, metallization, material consumption, and fabrication are required. Generally, solar cell contact structure includes emitter and base contact regions, such as contact diffusion regions, contacting conductive metallization—for example metallization connecting silicon in base and emitter contact areas through relatively heavy phosphorous and boron areas, respectively (for instance, for solar cells using n-type base region and p-type emitter region). Manufacturing cost and conversion efficiency factors are driving solar cell semiconductor absorbers ever thinner in thickness and larger in area, thus, increasing the mechanical fragility, solar cell power, and complicating processing and handling of these thin absorber based solar cells—fragility effects increased particularly with respect to crystalline silicon absorbers.
Current crystalline silicon (or other semiconductor absorber material) solar cell structures and processing methods often suffer from several disadvantages relating to cell bow and cell cracking/breakage during and/or after cell processing as well as during the operation of crystalline silicon PV modules installed in the field. Solar cell processing often induces significant process and material induced stresses (e.g., thermal and/or mechanical stresses) on a semiconductor substrate which may lead to thermally-induced warpage and crack generation and propagation (by thermal cycling or mechanical stresses). Bowed or non-planar solar cell substrates pose significant challenges and possible manufacturing yield degradation during solar cell processing (such as during processing of crystalline silicon solar cells), and may also present requirements for clamping down the solar cell substrate and/or the substrate edges onto a supporting substrate carrier to flatten the cell substrate during manufacturing process. Flattening solutions may complicate the solar cell manufacturing process resulting in increased manufacturing cost and/or some manufacturing throughput and yield compromises. Bowed or non-planar solar cell substrates may further result in cell microcracks and/or breakage problems during module lamination and also subsequently during the PV module operation in the field (resulting in PV module power degradation or loss). These problems may be further aggravated in larger area solar cells, such as the commonly used 156 mm×156 mm format (square or pseudo square) solar cells.
Further, conventional solar cells, particularly those based on an interdigitated back-contact or IBC design, often require relatively thick metallization patterns—due to the relatively high cell electrical current which must be extracted and delivered from the solar cell—which may add complexity to cell processing, increase material costs, and add significant physical stresses to the cell semiconductor material. Thermal and mechanical stresses induced by relatively thick (e.g., in the thickness range of 10's of microns for IBC cell metallization, for instance, about 30 to 100 microns of copper or aluminum) metallization patterns on the solar cell frontside and/or backside, coupled with the coefficient of thermal expansion or CTE mismatch between conductive metals (e.g., plated copper used for IBC solar cells or screen-printed aluminum-containing and/or silver-containing metallization pastes used for conventional front-contact solar cells) and semiconductor materials (e.g., thin crystalline silicon absorber layer) may substantially increase the risk of producing microcracks, cell breakage, and cell bowing during cell processing (i.e. during and after cell metallization) and module processing (during and after cell-to-cell interconnections and module lamination assembly) as well as during field operation of the installed PV modules (i.e. due to weather conditions, temperature changes, wind-induced and/or snow-load-induced and/or installation-related module bending stresses).